Power controller



July 26.192?. Y

J. G. MACLAREN PbwEn CONTROLLER July 215,1927.

J. G. MACLAREN POWER C ONTROLLER Filed March 26, 1926 E Sheets-Sheet 2 July 26 1927.

J. G. MACLAREN POWER CONTROLLER FiledA March 26, 1926 :s sheets-sheet 3 Patented July 26, 1927.

TATES PATENT OFFICE.Y

JAMES G. MACLAREN, OF SYRACUSE, NEW YORK, ASSIGNOR TO THE LAMSON COM- PANY, 0F SYRACUSE', NEW YORK, A CORPORATON 0F MASSACHUSETTS.

POWER CONTROLLER.

Application filed March 26, 1926. Serial No. 97,562.

This invention pertains to vpneumatic despatch .system of the socalled minimum flow vacuum type and relates more particularly to automatic power controlling appaiatus for use in such a syste-m.

Power control apparatus of this general character is disclosed in the patent to Libby No. 968,576. dated August 30, 1910. The patented apparatus provides automatic' pref:- sure actuated means for initiating a carrier impelling air flow through the transmission tube whenever a .carrier is entered therein as well means for cutting ott such flow after the lapse .of a predetermined period of time. lVhile l regard the patented device as generally correct in principle and highly effective in practice, I believe it preferable to have the cessation of carrier impelling air flow depend directly upon the discharge of the carrier from the delivery end of the tube rather than upon the operation of a timing device, and the principal object of this invention is to provide an .improved power control apparatus comprising means actuablc automatically upon insertion of a carrier within the despatch terminal to initiate low ot' the aii/ propelling current and also o perating automatically when t-lie last carrier emerges from the delivery terminal to cut oi'f the air current abruptly.

In the accompanying drawings I have disclosed one preferred embodiment of the inrcntion by way of example;

Fig, l being a fragmentary elevation illustrating part of the central station .desk of a pneumatic def-patch system having the irriproved power control apparatus applied thereto;

Fig. Q is a vertical section to larger scale through the casing oitl the improved power control apparatus showingI the several parts in the position which they assume when the transmission tube is empty;

Fig. 3 is a view similar to Fig. 2 but showing the parts in the position which they assume immediately after a carrier has been inserted in the transmission tube;

Fig. 4 is a similar view showing the parts in the position which they occupy soon after flight of the carrier has been initiated but before the carrier discharges;

Fig, 5 is a similar View showing the parts in the position which they occupy at the instant after discharge of the last carrier from the transmission tube;

Fig. 6 is an elevation looking from the left hand sidel of Fig. 4;

Fig'. 7 is an elevation, partly in section, looking from the right hand side of Fig. 4;

Fig. 8 is a fragmentary front elevation of the control apparatus,l certain parts being broken away and in section; Y i

Fig. 9 is a fragmentary vertical section substantially on the line 9-9 of Fig. 2;

Fig. l0 is a fragmentary detail view similar to Fig. 2 but illustrating a modification; and

Figs. ll and 12 are fragmentary sectional views illustrating further modifications.

Referring to the drawings, the numeral l indicates a fragmentary portion of the central station desk of a pneumatic despach system comprising transmission tubes, such, for example, as the tube 2, which lead from the central station desk to remote sending or clerks stations. Each tube is furnished with a delivery terminal 3 and is provided with a continuation l connecting it to the casing 8 of an individual power control device indicated generally by the numeral 5. This power control device is connected in turn by means of a suction tube 7 to a vacu um drum or header 9 in which a low pressure is continually maintained by ineansof a suitable pump, exhauster, or equivalent apparatus not shown.

An open-ended despatch terminal 6 is provided at the central station for each of the transmission tubes Q, such despatch terminal forming the entrance to that run of the tube which leads to the corresponding remote sending station. The above arrangement in general is old and well known in this art, and further details of such general arrangement are, therefore, unnecessary, the present invention being confined to improvements in the power control apparatus per se.

The iinpioved power control apparatus as herein disclosed comprises a hollow casing 8 having suitable openings at its top and bot tom for the reception of the ends of the tubes 4 and 7 respectively, and preferably has a removable door 8a covering an aperture in its wall. This casing divided by an internal septum into an inlet chamber 11 communicating with the tube t and an outlet chamber 12 communicating with the tube 7. The septum 10 is provided with a large valve aperture 13 of suiicient capacity to permit full carrier impelling air tlow to pass from lthe chamber' 11 to the chamber 12.

chamber 11 by means of an orifice 21, while the space 22 between the diaphragm and the cover member 18 normally communicates with'the outer atmosphere by means ot a port The cover 1S is provided with an outstanding lug or bracket 2l providing a pi votal support for a lever 25 which supports an auxiliary valve 26l adapted at certain times to close the port 28 and thus to cut ott communication between the chamber 22 and the outer atmosphere.y Preferal'ily the lever 25 is extended beyond its pivotal support to provide an arm carrying av counter-weight 26.

The chambers 15 and 22comn1unicate at all times by means of a restricted passage 2T controlled by a needle valve 2S. This needle valve may be adjusted from the outside ot the casing and determines Athe rate of tlow of air from one side of the diaphragm to the other.

The cover 18 is preferably provided with a central boss 29 having a guide opening therethrough and the wall 14 ot' the easing is turnished with a thickened part/30 having a guide opening aligned with the opening in the boss 29. A stem rod, or valve actuatingr element 31 slidesvtreely in the openings in the parts 29 and 30. This stem is lixedly secured to the central part of the diaphragm by means ot Aa suitable clamping device 82. The stem projects outwardly beyond the cover 18 and is encircled by a compression spring 33 bearing' at one end against the boss 29 and at its other against an abutment member 34 which is held v in adjusted position on the stem by means ot a nut 35 engaging the screw-threaded outer end of the stem. By adjusting thisv nut the tension of the spring 33 may be varied, the spring tending at all times to maintain the diaphragm in the position shown in Fi 2.

A bracket 3G is adjustably mounted upon the outer end of the stem 31 by means of suitable adjusting nuits 37, A light tension spring 38 is attached at one end to the bracket 36 and at its other to a pin 38 projecting from the end of the lever 3:3. These parts are so proportioned that when the diaphragm occupies the position of Fig. 2 the auxiliary valve 26 will also occupy the position shown in Fig. 2'unlcss 'forcibly held in another position ashereinaltcr described.

The inner end of the stein 251 is furnished with a stop collar 3S) adapted to abut the member 8() andjtoblimit outward movement of the stem by the spring 33. The inner end el() ot the stem is normally disposed closely adjacent to the under surtace ot a pivoted controlling valve Ll1 which governs the flow of air through the aperture 13 and which is supported at its lower end upon a shaft 42 journaled at its opposite ends in the walls of the casing. The valve is iixcdly secured to this shaft in any desired manner. and the valve may be of any suitable (,onstruction` but is preferably of sheet metal reinforced by ribs or otherwise to make it sufficiently still".

The shaft 42 projects beyond the front, wall of the casing (Figs. 9 and 10)v and is encircled by a coiled spring 43 ot clock spring type, the inner end of which is at;- tached to a sleeve 44 adjustably secured to the shaft 42 by means ot a set screw Al5. The outer end of the spring 123 is anchored to a post 46 projecting troni the wall ol the casing. Preferably the. spring is enclosed by a cap or cover el? having slotted cars it engaging set screws 49 projecting troni the vall ot' the casing S. By loosening these screws the cover may be removed toiexposu the spring for repairs or for zuljustment. ol its tension. This latter may be 'accomplished by looseningl the set screw l5 and turning the sleeve il relatively to the shaft 42.

For protecting the auxiliary valve 3G and the parts associated therewith l prefer to provide the cover 18 with a hollow cap 18 removably secured in position in the same way as the cap 4-7 just described, the cap 19 being lprovided with an opening 1S" preferably aligned with the end ot the stein 31 and adapted to allow free entrance of air to the space within the cap.

The valve -l1 is furnished with a downwardly directed toe 50 which engages the end oit an adjusting screw 51 when the valve is in closed position. This screw is normally so adjusted that when the valve is in closed position it is spaced a short distance from its seat at the edge of the orifice 13, thus permitting a small How of air from the chamber 11 to the chamber 12. This small How f constitutes the minimum flow socalled. If preferred. this minimum flow may be provided by means of an opening through the lower part of the septum l() or by a pipe exterior to the casing connect- Htl IuO

ing the chamber 11 with the suction tube, but I prefer the present arrangement since it permits adjustment of' the minimum flow from the exterior of the casing in a very simple manner.

The loe 5() furnished with a contact portion which, when the valve is closed as shown in Fig. 2. disposed to the left oi the vertical plane through the pivotal axis of the valve 41. vWhen the controlling valve closed this contact element 52bears against a latch spring 53 secured to the bottom wall of the casing and which may be adjusted by means of a screw 54. The coiled spring 43 so tensioned that it tends to open the valve 41, but when the valve is closed as shown in Fig. 2 the differential air pressure at opposite sides of the valve is normally sufficient to keep the valve closed until some positive force is applied for opening it. The latch 'spring 53 is so adjusted that when the exhauster is shut down the spring 43 will not throw the controlling valve open. lhile the latch spring is desirable for the reasons just stated. it is not essential to the normal. operation of the device.

Vv'hen the valve 41 is open, it engages the inner end of' a stop screw 55 adjustable from the outs-:ide ol the casing. This screw is so adjusted thatwhen the valve is wide open it stands in an inclined position with its free edge directed toward the oncoming air current. Tension of the spring 43 is such that it holds the valve in this open position after having been opened, during the flight of the carrier and in opposition to the force oli the flowing air current actingr upon the upper or lett hand side of the valve as viewed in the drawings.

ln Fig. 1() a slight modification et the apparatus is disclosed, and in this ligure 3,1 designates the valve stem having the stop collar 39" mounted thereon. The controlling valve 41 is provided on its under surface with a latch finger 56 adapted to engage the toe 57 ot a latch lever pivoted at 58 and provided with a counterbalance This latch lever is also furnished with an arm 30 ena geable bv the collar 39a so that as the simu 31" is moved to the left the latch lever swung. thus disengaging the member 57 from the member 56 and permitting the valve to open.

ln the modified arrangementshown in Fig. 11 the toc 52a of the valve 41 is so shaped that when the valve is vride open a flat surface of the toe bears against the spring 53 thus assisting or replacing the spring 43 for holding the valve open.

A ln Fig. 12 a modified arrangement for adiusting the tension of spring 43 is illuslrated. In this arrangement the outer end 60 of the spring 43 is attached to the end of an arcuate adjusting bar 61 concentric with the shaft 42 and having an arcuate slot for the reception or" guiding and retaining screws 62 and (S3 which enter threaded openings in the wall of the easing 8. After loosening these screws the bar G1 may be moved endwise, thus varying the tension of the spring. l

The operation of the device shown in. Figs. 1 to .9 `is substantially as follows, it being assumed that when the transmission Vtube is empty the parts occupy the position shownV in F 2 and that at this time a suitable vacuum or low pressure is maintained in the suction tube 7, thus causing a minimum flow of' air from'the open end (5 of the transmission tube 2 throughout the length ot' such tube and through the tube 4 and chambers 11 and 12 to the suction tube 7.

lVhen a Vcarrier is inserted in the transmission tube the minimum flow is cut off or reduced and the pressure in the chamber 11 drops due to the withdrawal of air there- 'from through the minimum flow orifice or passage. This reduction in pressure in the chamber 11 is sufficient to move the diaphragm 17 to the left until it occupies the position shown in Fig. 3. During the early part off this movement the port 23 is open thus permitting atmospheric pressure to act freely upon the right hand side of the diaiihragm 17. As the diaphragm moves to the left the end 40 of the stem 31 pushes the valve 41 over to its open position as indicated in Fig. 3 and near the end of this movenient the auxiliary valve 26 is swung up until it closes the port 23.

The carrier now takes up its flight through the transmission tube and during its flight the air is gradually sucked out of the chainber 22 through the passage 27 until the` pressures at opposite sides of the diaphragm 17 are substantially balanced. For the proper operat-ion of the device the needle valve 2S is so set that this balancing of pressure may take place prior to the delivery of the carrier from the tube, and of course the setting of this valve will depend to some extent upon the length of the transmissiontube, the condition of the tube and carriers, and the suction maintained by the exhauster.

As soon as the pressures are substantially balanced upon opposite sides ot the diaphragm'. the spring 33 returns the dia.- phragin to its normal position as indicated in Fig. 4, leaving the controlling valve wide open since there is no positive connection between the diaphragm stem and the valve. The valve is now maintained in this open position by the tension of the spring 43. which, as above stated. is so adjusted as to hold the valve in this position during the entire flight of the carrier. However, when the lastcarrier emerges from the transmission tube a` sudden rush of air through the tube ensues and when this rush ci air strikes the upper Surface 40f the valve 41 the latter Lil lidi? Al l) is suddenly swung back to its closed position. The valve is free to swing at this time since the stem 31 has previously been retracted as above described, and when the valve reaches its closed position, it is retained there by the suction on the under side of the valve.

Then the diaphragm returns to the position shown in F ig. 4, it tends also to open the auxiliary valve 26, but since the chamber 22 is at this time substantially under suction tube pressure, the atmospheric pressure acting upon the outside of the auxiliary valve 26 holds it firmly against its seat, and as t-lie stem 31 moves to the right the spring 38 is stretched as shown in F ig. 4, thus storing up energy. v

After the controlling valve 41 has returned to its seat, as shown in Fig. 5, the chamber is cut off from full suction tube pressure so that the pressure in the chamber 22 then rises by leakage through the passage 28 until the pressures upon opposite sides of the auxiliary valve 26 are so nearly equalized that the stored up energy in the spring 38 is suflicieiit to open the auxiliary valve 23. thus restoring the parts to their original position.

From' consideration of the above operation it will be evident that while the controlling valve 41 is opened positively in response to the pressure change resulting from introduction of a. carrier into the tube, it is in no way directly influenced b v the return of the actuating pneumatic or diaphragm, and remains fully open until the discharge of the Alast. carrier from the tube, when it is then directly closed by the vair rush which takes place at the instant of delivery. y

The device illustrated in Fig. 10 operates substantially as above describedr except that a positive lock is furnished for retaining the controlling valve in closed position. Vith such an arrangement the tension of the spring 43 may if desired be such as to open the valve without any direct push from the diaphragm stein 31, the latter merely acting to release the latch member 57 from the member 56. i

While certain preferred embodiments'of the invention have herein been shown by Yay of example, it is to be understood that various changes in the proportions and 'ar--r rangements of parts may be made if' desired kand that equivalent parts may be substituted for those here shown or in some instances that certain parts may be omitted without departing from the spirit of the invention, and further that while the actuating pneumatic has been shown and describedfas a flexible diaphragm, any other suitable device` for example, a piston, may be substituted therefor.

I claim:

1. Power control apparatus `tor a pneumatic despatch system of the minimumeow type having a transmission tube and means for creating carrier propelling air flow therein, said apparatus comprising a normally closed controlling valve, a minimum flow through the tube being permitted when."

the valve is closed, and a pneumatic for opening the valve in response to reduction in pressure in the transmission tube due to introduction of a carrier therein, said valve closing by the direct action of the air current thereagainst when the carrier is delivered from the tube.

2. Power control apparatus of the minimum flow type having a transmission tube, an exhauster, and a controlling valve for governing carrier impelling air fiow through the tube, a minimum flow of air through the tube being permitted when the controlling valve is in closed position, said apparatus comprising a pneumatic responding to pressure reduction in the tube due to introduction ot a carrier therein, and by such response opening the valve', the pneumatic being movable back to its normal position independently of the valve, the valve being returned to closed position solely by the action thereagainst of the flowing air current.

3. Power control apparatus for a pneumatie despatch system of the minimum flow tvpe having a transmission tube and means for creating carrier propelling air flow therein, said apparatus comprising a normally closed controlling valve. a minimun'l flow through the tube heilig permitted when the valve is closed, and a pneumatic for opening the valve in response to reduction in pressure in the transmission tube due to introduction ofa carrier therein, the valve being pivoted adjacent to one edge and when open standing in inclined position with its free edge directed toward the air current, said valve closing by the direct action of the air thereagainst when the carrier is delivered from the tube.

4. Power control apparatus for a pneumatic despatch s vstem of the minimum flow type having a transmission tube and means tor creating carrier propelling air flow therein, said apparatus comprising a normally closed controllingvalve, a minimum fiow through the tube being permitted when the valve is closed, and a pneumatic for opening the valve in response to reduction in pressure in the transmission tube due to introduction of a carrier therein, the valve tending to close in direct response to the air current flowing over itssurface, and means independent of' the pneumatic for holding the valve open so long as a carrier remains in the tube.

5. Power control apparatus for a pneumatic despatch system of the minimum fiow type having a transmission tube and means for creating carrier propelling air flow therein, lsaid apparatus comprising a norlul) .lill

` lil l.

mally closed controllingvalve, a minimum fiow through the tube being permitted when the valve is closed, and a pneumatic for opening the valve in response to reduction in' matic despatch system of the minimum flow type having a transmission tube, and an eX- liauster for creating a carrier impelling air flow through the tube, said apparatus comprising a controlling valve for governing such carrier impelling fion', said valve n ormally occupying a closed position, a minibeing permittedwhen the mum flow of' air valve is closed, means responsive to introduction of a carrier into the tube `for opening the valve, and independent means for holding the valve open during the Hight of the carrier.

T. Power control apparatus for a pneumatic d 'patch system oit the minimum flow tipe hav ,ig a transmission tube, and an eX- hanster ior creating a carrier impellingl air flow through the tube, said apparatus coma controlling valve for governing rriei' impelling flow, said valve noroctaipving a closed position, a mini- 'flow of air being permitted when the 'valve is closed, means responsive to introduction of a carriage into the tube for opening the valve, and a spring for holding the valve open during the flight of the carrier.

el. Power control apparatus for a pneumatic desil atch system ot' the minimum flow type having a transmission tube, and an exhale-:ter for creating a carrier impelling air flow through the tube, said apparatus comprising a controlling valve 1to1' governing such carrier impelling flow, said valve normally occupying a closed position, a minimum flow ot' air being permitted when the valve is closed, means responsive to introduction ot' a carrier into the tube for opening the Yalve, a spring for holding the valve open during the flight of the carrier, and means toi' adjusting the spring to vary the force exerted thereby.

fl. Power control apparatus for a pneumatic despatch system of the minimum fion' type having a transmission tube and means ilor creating a carrier impelling air fioiv tin'ough the tube, said apparatus comprisimf a controlling valve i'or governing` such the controlling valve normally cutting carrier impelling flow, a minimum flow 'gong i the tube norn'iall y being permitting, prr-umatic vwhich advances in response to dermis; in pressure in the tube' due to intromal lv duction off a carrier therein and thereby opens the valve, and means independent of the pneumatic for holding the valve openv during the iiight of the carrier.

l0. Power control apparatus for a pneumatic despatch system oit the n'iinimum flow having a transmission tube and means creating a carrier impelling airV fiow turough the tube, said apparatus comprising a coiitrolling valve for governing suoli flow,-

the controlling valve normally cutting oit carrier impelling flow, a minii'num fiow through the tube normali)7 being permitted,

a pi'ieumatic which advances in response to decrease in pressure 1n the tube due to 1n- `traduction ot' Va carriei' therein and thereby opens the valve, `the pneumatic retreating substantially to normal position prior to delivery oil the carrier, and means t'or retaining the valve in open position during the flight ot' the carrier. i a

1l. Power control apparatus 'for a pneumatic despatch system ot' the minimum flow type having a transmission tube and means for creating a carrier in'ipelling air flow through the tube, said apparatus comprising a controlling valve for governing such floiv, the controlling valve normally cutting ofl carrier impelling fiow, a minimum fiony through the tube normally being permitted, a pneumatic which advances in response to decrease in pressure in the tube due to introduction of a carrier therein and thereby opens the valve, the valve When open exposing a surface to the flowing air current such that the valve tends to close, means causing the pneumatic to retreat subsumtially to normal position during the flight of the carrier, and yielding' means for holding the valve in open position during flight of the carrier. l

l2. Poiver control apparatus for a pneumatic despatch system ot the minimum lionv type having a transmission tube and means for creating a carrier inipelling air floiv through the tube, said apparatus comprising' a controlling valve for governing such flow, the controlling valve normally' cutting oit' cari'ier impelling flow, a minimum flow through 'the tube normally being permitted, a pneumatic which advancesin response to decrease in pressure in the tube due to introduction ot a carrier therein and thereby opens the valve, the valve when open standing in such position relatively to the ail' current that the flowing air tends to close the valve, means for moving the pneumatic back substantially to its normal posit-ion prior to delivery ot the carrier, and n'ieans holding the valve open during flight oi the carrier but permittingit to close in response to the sudden rush ot air following delivery of the carrier from the tube.

13mm Power control apparatus for pneumatic despatch system of the minimum flov;

lll)

forereating a carrier impelling air flow through the tube, said apparatus comprising .ya controlling valve for governing such iiow,

the controlling valve normally cutting ott1 carrier impelling How, a minimum iiow 'through the tube normally being permitted, a pneumatic which advances in response to decrease in pressure in theftube due to introduction of a carrier therein and thereby opens the valve, the valve being pivotcd to swingend when open being inclined to the flowing air with its free edge directed toward the air current so that the current tends to close the valve, means causing the pneumatic to retreat prior to delivery oi the vcarrier from the tube, and a springV device for holding the valve open until the carrieris delivered from 'the tube.'

14. Power control apparatus for a pneumatic despatch system ot the minimum How type having a transmission tube, means for creating carrier impelling air tlow therein, and ay controlling valve for Vgoverning carrier impelling `air flow, a minimum `flow of air being permitted when the valve is in closed position,said apparatus comprising a4 valve actuator having a non-positive engagement with the valve, said actuator when moving in one direction opening the valve andy when moving in 'the opposite direction being ineffective to change the position of the valve. i

l5. Power control apparatus of the minimum ow type having a transmission tube, an exhauster and a controlling valve for governing carrier impelling air How through y the tube Y a minimum flow of air throuvh the tube being permitted whenthe controlling valve is in closed position, said apparatus comprising a pneumatic which moves in one direction in response to introduction ot a carrier into they tube and thereby opens the controlling valve, the pneumatic returning to normal position without closing the controlling valve. f

16. Power `control apparatus for a pneumatic despatch system of the minimum ow type having a transmission tube, meansfor creating carrier impelling air flow therein, and a'controlling valve for governing carrier impelling air flow, a minimum flow of air being permitted when the valve is in closed position, said apparatus comprising a valve actuating member, a pneumatic for moving said member in one direction to open the valve, and means yfor restoring lthe pneumatic to normal position independently of the valve., 1

17. Power control apparatus of the minimum flow type having a transmission tube. an exhauster and a controlling valve for governing carrier impelling air iiow through the tube, a minimum iiow of air through the site direction.

tube being permitted when the controlling valve is in closed position, said apparatus comprising a pneumatic which moves in one direction in response to introduction of a carrier into the tube and thereby opens the controlling valve, and a spring for moving the pneumatic in the opposite direction, the

pneumatic moving inl thelatter direction rection but which is ineffective `to move the valve when it reciprocates in the opposite direction.

19. Power control apparatus ot the minimum iiow type having a transmission tube, an exhausler, and a controlling valve for governing carrier impelling air flow through the tube, a minimum liow of air through the tube being permitted when the controlling valve is in closed position, said apparatus comprising a pneumatic and a valve opener connected to the pneumatic, said valve opener being aranged to engage the controlling valve and to push the valve open as the pneumaticmoves in one direction, said valvev opener retreating frrely from the valve'as the pneumatic returns to normal position, leaving the valve open.

20. Power control apparatus for a pneumatic despatch system ot the minimum How type having a transmission tube, means for creating carrier impelling air How therein, and a controlling valve for governing carrier impelling air flow, a minimum flow ot air being permitted when the valve is in closed position, said apparatus comprising a reciprocating bar, a pneumatic for moving the bar in one direction, and independent means for moving the bar in the opposite direction, movement of the bar in one direction opening the valve, the bar moving in the opposite direction independently of the valve.

21. Power control apparatus of the minimum flow type having a transmission tuba` an exhauster, and a controlling valve for governing carrier impelling air flow through the tube,a minimum flow of air through the tube being permitted when the controlling valve is in closed position, said apparatus comprising a pneumatic having a reciprocating stem, the stem being arranged to cngage the controlling valve and to open the latter as the diaphragm moves in one direction and to move freely away from said valve as the diaphragm moves in the oppo- 22. Power control apparatus for a pneumatic despatch system of the minimum tlow type having a transmission'tubc, means for creating carrier impelling air flow therein, and a controlling valve tor governing carrier impelling air flow, a minimum flow of air being permitted when the valve is in closed position, said apparatus comprising a pneumatic moving in one direction in response to reduction in pressure in the tube due to introduction of a carrier therein, a spring for moving the pneumatic in the opposite direction, and a reciprocable stem t'or the pneumatic, one end of said stem pressing against the valve for opening the latter as the stem moves in one direction and disengaging the valve as the stem moves in the opposite direction.

23. Power control apparatus i'or a pneumatic despatch system of the minimum flow type having a transmission tube, means for creating carrier irnpelling air flow therein, and a controlling valve for governing carrier impelling air flow. a minimum flow ot air being permitted when the valve is in closed position, said apparatus comprising a pneumatic responsive to introduction of a carrier into the tube, a valve actuatingr element connected to the pneumatic and normally engaging the valve, means for adjusting the normal position ot' said actuating member whereby to hold the valve spaced :from its seat to provide a minimum flow passage, and means for restoring the actuating element to normal position, said latter means being ineffective to move the valve.

24. Power control apparatus for a pneumatic despatch system of the vacuum minimum tloW type having a transmission tube, an exhauster for creating a carrier propelling air How through the tube, and a controlling valve for governing` such flow through the tube, said controlling valve normally occupying a closed position, a minimum flow of air being permitted when the valve is closed, said apparatus comprising means constantly tending to open the valve, such means being incapable of opening the valve while the transmission tube is empty, and means operative upon introduction of a carrier into the transmission tube for positively opening the valve.

Power control apparatus Ator a. pneumatic despatch system ot' the vacuum minimum tlovr type having a transmission tube, an exhauster for creating a carrier propelling air flow through the tube, and a controlling valve for governing such flow through the tube, tht` controlling valve normally occupying a closed position, a minimum flow of air being permitted when the valve is closed, said apparatus comprising means tending to open the valve in opposition to the suction produced by the exhauster, and pneumatic responsive to the reduction in minimum flow through the tube incident to insertion olla carrier therein tor positively opening the valve.

Power control apparatus for al pneumatic despatch system ot the vacuum minimum flow type having a transmission tube, means for creating a carrier propelling air flow therethrough, and a controlling valve for governing such flow through the tube, a minimum `tlow being permitted when the valve is in closed position. said apparatus comprising a spring tending t-o open the valve, the latter normally being in closed position, and means assisting the spring to open the valve when a carrier is introduced into the transmission tube.

27. Power control apparatus for a pneumatic despatch system of Athe vacuum minimum flow type having a transmission tube,

an exhauster tor creating a. carrier propelling air flow through the tube, and a controlling `valve 'for governing such Aflow through the tube, the controlling valve normally occupying a closed position, a minimum flow ot air being permitted when the valve is closed` said apparatus comprising a spring tending to open the valve in opposition to the suction produced by the` eX- hauster, and a pneumatic responsive to reduction in pressure in the tube due to insertionr of a carrier therein for assisting the spring in opening the valve.

2S. Power control apparatus for a pneumatic despatch system of the vacuum minimum flow type having a transmission tube, means y'for creating a carrier propelling air flow therethrough, and a controlling valve for governing such flow through the tube, a minimum. flow being permitted when the valve is in closed position, said apparatus con'iprising retaining means normally holding the valve in closed position, and a pneumatic tor releasing the valve from the retaining means.

29. Power control apparatus for a pneumatic despatch system of the vacuum minimum low type having a transmission tube, means for creating a carrier propelling air flow therethrough, and a controlling valve for governing such `tlow through the tube. a minimum flow being permitted when the valve is in closed position, said apparatus comprising means tending to open the valve, means normally retaining the valve in closed position, and means for releasing the valve :trom the retaining means.

30. Power control apparatus Jfor a pneumatic despatch system ot the vacuum minimum flow type having a transmission tube, means for creating a carrier propelling air flow therethrough, and a controlling valve for governing such flow through the tube, a minimum flow being permitted when the alve is in closed position, said apparatus comprising means for opening the valve, and

lll() mechanical means normally holding the controlling valve in closed position.

3l. Power control apparatus for a pneumatic despatch system of the vacuum minimum flow type having a transmission tube, means for creating a carrier propelling air iow therethrough, anda controlling valve for governing such flow through the tube, a minimum flow being permitted when the valve is in closed position, said apparatus comprising releasable means for latching the controlling valve in closed position.

32. Power control apparatus for a pneumatic despatch system of the vacuum minimum tiow type having a transmission tube, means for creating a carrier propelling air flow therethrough, and a controlling valve for governing suchtlow through the tube, a minimum `flow being permitted when the valve is in closed position, said apparatus comprising a latch normally holding the valve in closed position, and means for releasing the latch to allow the valve to open.

33. Power controly apparatus for a. pneu-v matic despatch system ot' the vacuum minimum flow type having a transmission tube, means for creating a'carrier propelling air iiow therethrough, and a controlling valve 'for governing such fiow through the tube, a minimum flow being permitted when the valve is in closed position, said apparatus comprising a spring latch normally retaining the controlling valve in closed position.

34. Power control apparatus for a pneumatie despatch system of the vacuum minimum flow type having a transmission tube, means for creating a carrier propelling air flow therethrough, and av controlling valve for governing such flow through the tube, a minimum flow being permitted when the 'alve is in closed position, said apparatus comprising a pneumatic for opening the valve in response to introduction of a carrier into the transmission tube, and latch means normally holding the valve in closed position, said latch means releasing the valve to permit it to open freely after a predetermined movement ot the pneumatlc.

35. Power control apparatus tor a pneumatic despatch system of the vacuum minlimum flow type having a transmission tube,

means for creating a carrier propelling air flow therethrough, and a controlling valve for governing such flow through the tube, a. minimum flow being permitted when the valve is in closed position, said a paratus comprising a latch normally hol ing the valve in closed position, and means for adjustably determining the force necessary to release the valve from the latch.

36. Power control apparatus for a pneumatic despatch system of the vacuum minimum flow type having a transmission tube, means for creating a carrier propelling air flow therethrough, and a controlling valve for governing such flow through the tube, a minimum flow being permitted when the valve is in closed position, said apparatus comprising a spring latch normallj1 holding the valve in closed position, and means for adjusting the tension of said spring whereby to determine the force necessary to release the valve from the latch.

37. Power control apparatus for a pneu-` matic despatch system ot thc vacuum minimum flow type having a transmission tube, means for creating a carrier propelling air How therethrough, and a controlling valve tor governing such liow through the tube, a minimum tlow being permitted when the valve is in closed position, said apparatus comprising a pivotal support for the valve, the valve being provided with a latch engaging toe, and a resilient latch member .normally engaging said toe and tending to retain the valve in closed position.

23S. Power control apparatus tor a pneumatic despatch s vstem oi the vacuum minimum l'low type having a transmission tube, means lor creating a carrier propelling air flow therethrough, and a controlling valve tor governing such flow through the Lube, a minimum tlow being permitted when the valve is in closed position, said apparatus comprising a pivotal support for said valve adjacent to one side of the valvca latch engaging toe projecting to the opposite side ot' the pivotal support from thc main body ot' the valve, and a spring latch, the toe oi the valve normally engaging the latch at such a point relatively to the pivotal supportas to tend to keep the valve in closed position.

3S). Power control apparatus for a pneumatic despatch system oi the vacuum minimum liow type having a transmission tube, means for creating a carrier propelling air flow therethrough, and a controlling valve for governing such ilow through the tube, a minimum liow being permitted when the valve is in closed position, said apparatus comprising a pivotal support l'or the valve. the. main body ot the valve when in closed position extending to one .side ol' the vertical plane through the pivotal support, a loe member projecting in the opposite direction lfrom the main body ot thc valve, and a spring latch normally engaging said tor at a point at the other side of said vertical plane from that at which the main body of the valve is situated thereby tending to retain the valve in closed position.

10. Power control apparatus l'or a pneumatic despatch system of the vacuum minimum flow type having a transmission tube, means for creating a carrier propelling air flow therethrough, and a controlling` valve for governing such flow through the tube, a minimum liow being permitted when the valve is in closed position, said apparatus ,lili

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comprising means tending to open the valve, releasable latch` means normally retaining th'e valve inclosedposition,and means for releasing the valve from the retaining means.

41. Power control apparatus tor a` pneu.- matic despatch system or'rthe vacuuinminimum-flow type having a transmission means tor creatingacarrier propelling air low therethrough, and a controlling valve for governing such flow throughl the tube, aniinimum low being permitted when the valve is in` closed position, saidl apparatus comprising.means tending vto open the valve, releasable latch means normally retaining the valve in closed'position, and a pneumatic responsive to reduction in the minimum flow through the transmission tube and by its response releasing the valve irom the retaining .means 42. Power controlv apparatus for pneumatic despatch systems of the minimum flow type havinga transmission tube, an exhauster, and a valve for controlling carrier impelling air flow through the tube, said apparatus comprising a casing, a `diaphragm dividing said casingfinto two chamb`ers,.on`e chamber connnunicating withithe transmission tube and the other by means of a port with the outer atmosphere, an auxiliary valve for closing said port, and means for transmitting movement of the diaphragm in one directionto the auxiliary valve but permitting the diaphragm to return to its original position independently of the auxiliary `valve. v

43. Power controlapparatus t'or a pneumatic despatch system ofl the minimum low type having a conduit, means for creating a carrier impelling air flow in the conduit, and a controlling valve for governing cai'- rier `impelling flow through they conduit, a minimum flow of' air through the 4conduit being permitted when the if'ailve is in closed` position, said apparatus comprising aV pneumatic exposed at one side to the pressure in said conduit and normally exposed at4 its other side to atmospheric pressure, the pneumatic responding to introduction ot' a carrier into the conduitand in so responding opening'the valve, and means actuated by the pneumatic for cutting' otl the pneumatic from atmospheric pressurewhen the valve opens, said means keeping. the pneumatic cut oil from atmospheric pressure until vafter the pneumatic has been restored to normallposition.

44. Power control apparatus for pneumatic despatch systems of theminimum flow ty pe having a; transmissionA tube, an exhauster, and a valve 'for controllilng carrier imair flow through the tube, said apparatus`- comprising a casing,A a diaphragm dividing said casing into two chambers,` one chamber' communicating with thetransmis- A sion tube and the other171V means eta 'portl -pelling air ilowi with. the outer atmosphere, an auxiliary valve for closing said. port, andconnections between the diaphragm and auxiliary valve for actuatingv the latter, said connections coi'nprising a yielding member permitting atull movement ot the diaphragm in one direction without moving the auxiliary valve'.

45. Power control apparatus tor pneumatic despatch systems of theminiinum flow typey having a transmission tube, an exhauster, anda valve for controlling carrier impellingair flow through the tube, said'apparatus comprising a,casing,.a diaphragm dividing said casing into two chambers, one chamber communicating `with the` transmission tube and the other by meansot aJ port with the-outer atmosphere, an auxiliary valve for closing said port,imeans for transmitting. movement ot the diaphragm in one direction to the controllingvalve, and con-nectionstransmittngsaid movement of the diaphragm to the auxiliary valve t-o close the latter, said connections permitting the diaphragm to move in the opposite` direction without opening the auxiliary valve;

46. Power con-trol apparatus for pneumatic despatchV systems of the minimum llow type havingV a transmission tube, an exhauster, and a valve for controlling carrier impellin-g. airowl through the tube, said apparatus comprising a` casing, a diaphragm dividing said casinginto two chambers, .one chamber communicating with the transmission tube and the other -by means of a port with the outer atmosphere, an auxiliary valve tor clsingsaid port,- and connections actuated'by the diaphragm asyit=moves in one directionto close said auxiliary valve, said' connections including a partk which stores up energy' as the diaphragm returns to normal'position and which opens the auxiliary `valve after the diaphragm has fully completed its return movement;l

47. Power cont-rol apparatus for pneumatie despatch systems of the minimum flow type havinga transmission tube, an exhauster, and a yvalve tur controllingcarrier inithrough the tube, said apparatuscomprising a casing, a diaphragm dividing. said =casingtinto two chambers, kone chamber communicatingwith ythe transmission tube andthe other by means ot Va port with the outerA atmosphere, an auxiliary valve for closing said port, means actuable by the diaphragm'as it moves in one direction to open the cont-rolling valve, and a spring for transmitting motion from said means to the auxiliary valve for closing the latter as the controllingvalve opens, the diaphragm returning to normalposition prior to closure of thev controllingvalve, the motion transmitting springstretching during retunmovement of the `diaphragm and b'ecoming operative to' open the auxiliary valve only after the Vcontrolling"valve has closed.

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'chamber communicating with sion tube andthe otl 48. Power control apparatus for pneumatic despatch systems of the minimum flow type having a transmission' tube, an exhauster, and a valve for controlling carrier impelling air flow through the tube, said apparatus comprising a'casing, a diaphragm dividing said casing into two chambers, one chamber communicating with the transmission tube and the other by means of a port with the outerl atmosphere, an auxiliary valve for closin said port, a stem for the diaphragm, said stem being arranged to Open the controlling valve as the diaphragm moves in one direction, a spring for restoring the diaphragm and its stem to normal position independently of the controllmg valve, and means including a yielding part connecting the diaphragm stem with the auxiliary valve, said latter means closing the auxiliary valvey when the diaphragm moves in one direction but yielding to permit the diaphragm to return to normal position without moving the auxiliary valve.

49. Power control apparatus for pneumatic despatch systems of the minimumflow type having a transmission tube, an exhauster, and a valve for controlling carrier impelling airflow through the tube, said apparatus comprising a casing, a dlaphragm dividing said casing into two chambers, one chamber communicating with the transmissiontube and the other by means of a port with the outer atmosphere, an auxiliary valve for closing sa'id port, a leverarm carrying said auxiliary valve, and means including a` tension spring connecting the lever with the diaphrag y.

50. Power control apparatus for pneumatic despatch systems of the minimum low type having a transmission tube, an exhauster, anda valve for controlling carrier impelling air How through the tube, said apparatus comprising acasing, a diaphragm dividing said casing into two chambers, one

the transmis- 1er by means of a port with the outer atmosphere, an auxiliary valve for closing said port, and means for transmitting movement of the diaphragm in one `direction `to `the `controlling valve for opening the latter and to the auxiliary valve -for closing it, said transmitting means permitting the diaphragm to return to rnormal position without closing the controlling valve or opening the auxiliary valve.

,'51. Power control apparatus for pneumatic despatch systems of the minimum liow `type having atransmission tube,y an exhauster, and av valve for controlling carrier nnpelllngiair flow through the tube, said apparatus comprising a casing, a diaphragm sion tube andthe other dividing said casing into twochambers, one chamber communicating with lthe transmisby means of a port with the outer atmosphere, an. auxiliary 'the controlling valve,

valve for closing said port, a valve actuating rod connected to the diaphragm, o ne end of the rod engaging the valve and opening the latter when the diaphragm moves in one direction, the rod being movable in the opposite direction independently of a spring tending to return the diaphragm to normal position, and means connecting the auxiliary valve to the valve actuating rod and adapted to close the auxiliary valve when the controlling valve opens, said connecting means yielding when the rod moves in the opposite direction to permit the auxiliary valve to remain closed.

52. Power control apparatus for a pneumatic despatch system of the minimum flow t-ype having a conduit, means for creating a carrier impelling air flow in the conduit, and a controlling valve for governing carrier impelling flow through the conduit, a minimum low of air through the conduit'l being permitted when the valve is in closed position, said apparatus comprising a casing divided into two chambers by a movable wall, one of said chambers communicating with the conduit and the other with the outer atmosphere by means of a normally open port, an auxiliaryr valve for closing said port, a stem connected to the movable wall, the wall moving in response to introduction of a carrier into the tube and by means ot its stem pushing the controlling valve open, means connecting the stem to the auxiliary valve ,to close the latter as the controlling valve is opened, means permitting the pressure upon opposite sides of the movable wall to become substantially balanced prior to delivery of the carrier from the tube, and means operative to restore the movable wall to normal position independently of the controlling valve when such pressures are substantially balanced, the auxiliary valve remaining closed after the movable wall has returned to normal position and until the controlling valve closes.

53. Power control apparatus for pneumatic despatch systems of the minimum flow type having a transmission tube, an exhauster, and a valve for controlling carrier impelling air flow through the tube, sa'id apparatus comprising a casing. a diaphragm dividing said casing into two chambers, one `chamber communicating with the transmission tube and the other by means of a port with the outer atmosphere, an auxiliary valve for closing said port, means providing a passage leading from one of said chambers to the other, a-valve actuating rod connected to the diaphragm, a spring tending to maintain the rod in inoperative position, and

means connecting the rod to the auxiliary valve, the diaphragm responding to introduction of a carrier into the transmission tube and thereby moving the actuating rod to push open the controlling valve and close the auxiliary valve, the passage between the chambers being of such capacity that after the controllinflr valve opens the pressure in the two cham ers is substantially equalized prior to delivery of the carrier from the tube, the spring then returning the actuating rod to normal position leaving the controlling valve open.

54. Power control apparatus for pneumatic despatch systems of the minimum flow type having a transmission tube, an eX- hauster, and a valve for controlling carrier impelling air flow through the tube, said apparatus comprising a casing, a diaphragm dividing said casing into two chambers, one chamber communicating with the transmission tube and the other by means of a port with the outer atmosphere, the casing hav- Aing a passage connecting said chambers, an adjustable bleeder valve controlling said passage, an auxiliary valve for closing the port leading to the atmosphere, a valve actuating rod connected to the diaphragm, one

end of the rod being disposed adjacent to the surface of the controlling Valve, means including a yielding element connecting the rod to the auxiliary valve, a spring tending to hold the rod in normal position, and means tending to hold the auxiliary valve in open position, the diaphragm responding to introduction of a carrier into the tube and thereby moving the rod to push the controlling valve open and to close the auxiliary valve, the bleeder valve being so set that after the controlling valve opens and before the carrier is delivered the pressure in the two chambers are substantially equalized whereby the diaphragm and rod return to normal position, the controlling valve remaining openv` and the yielding connection permitting the auxiliary valve to remain closed until the carrier is delivered from the tube.

Signed by me at Syracuse, New York, this fourth day of March, 1926.

JAMES G. MACLAREN. 

